Single FrAction Interstitial BreaSt BracHytherApy

Inclusion Criteria

• Female
• New diagnosis of Ductal Carcinoma in Situ (DCIS) and/or invasive breast carcinoma per histologic evaluation
• Age 40-85 at diagnosis
• Previous lumpectomy with surgical margins histologically free of invasive tumor and DCIS as determined by the pathologist
• T stage of Tis, T1, or T2
• T2 tumors must be ≤3 cm in maximum diameter
• If the tumor is human epidermal growth factor receptor (HER2)-positive, the patient is planning to receive or has already received HER2-directed therapy
• For patients with invasive breast cancer, an axillary staging procedure must be performed (either sentinel node biopsy alone or axillary dissection [with a minimum of 6 axillary nodes removed]) and the axillary node(s) must be pathologically negative Note: N0(i+) is not an exclusion criterion

Note: Patients meeting all of the following criteria are not required to undergo the axillary staging procedure:

• ≥70 years of age
• Estrogen receptor (ER)+, progesterone receptor (PR)+/-, HER2-
• Grade 1-2 breast cancer
• Tumor ≤2 cm in size

Note: If patients meet all the following criteria, the decision to avoid sentinel lymph node biopsy can be at the discretion of the breast surgeon:

• 50-69 years of age
• Grade 1-2 breast cancer
• Clinically negative axilla by ultrasound and/or magnetic resonance imaging (MRI)
• ER+, PR+, HER2-
• Tumor ≤2 cm in size
• Agrees to comply with aromatase inhibitor recommendation
• Ability to begin brachytherapy within 12 weeks following lumpectomy, re- excision of margins, or completion of chemotherapy
• Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria

• Pregnant or breastfeeding
• Active collagen-vascular disease
• Paget's disease of the breast
• Any prior history of DCIS or invasive breast cancer prior to the current diagnosis
• Any prior history of breast radiation therapy (RT) or thoracic RT for any condition
• Multicentric carcinoma (DCIS or invasive)
• Synchronous bilateral invasive or non-invasive breast cancer
• Surgical margins that cannot be microscopically assessed or that are positive
• Treatment with neoadjuvant chemotherapy
• Excision cavity that cannot be clearly delineated or is not amenable to implant per the treating investigator
• Medical, psychological, or social condition that, in the opinion of the investigator, may increase the patient's risk or limit the patient's adherence with study requirements